Fix: an issue after update RDF gem to 3.0 that frozen request params

[syphax-bouazzouni]

Changes

• fix an issue after update RDF gem to 3.0 that frozen request params (https://github.com/ontoportal-lirmm/ontologies_linked_data/commit/69d0ea3ae55d443303bd847e1d2de8b670a8dc1c)
• handle the case when the SPARQL endpoint default value is empty (https://github.com/ontoportal-lirmm/ontologies_linked_data/commit/603a3806cc333a6b94d22617d8d5a1af979b7766)

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 80.12%. Comparing base (c9b8b42) to head (603a380).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## development #133 +/- ## =============================================== + Coverage 79.94% 80.12% +0.17% =============================================== Files 84 84 Lines 6133 6138 +5 =============================================== + Hits 4903 4918 +15 + Misses 1230 1220 -10 ``` | [Flag](https://app.codecov.io/gh/ontoportal-lirmm/ontologies_linked_data/pull/133/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ontoportal-lirmm) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/ontoportal-lirmm/ontologies_linked_data/pull/133/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ontoportal-lirmm) | `80.12% <100.00%> (+0.17%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ontoportal-lirmm#carryforward-flags-in-the-pull-request-comment) to find out more.

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